(1) Field of the Invention
The invention relates to a charge valve for gas, in particular for carbon dioxide, comprising more particularly a seat drilled with a passage, a shaft movable inside the passage against the compression of a return spring bearing against the seat and an elastomeric seal compressed between the seat and the shaft to close the passage when the shaft is moved into a first closed position, called low-pressure position.
(2) Prior Art
Such a charge valve is known from document U.S. Pat. No. 6,637,726 relating to an air conditioning system using carbon dioxide CO2.
In the low-pressure closed position, that is for gas pressures up to 60 bar, the elastomeric seal is sufficient to tightly close the passage. However, the force on the shaft increases with an increase in the gas pressure, which may be up to 200 bar. This causes a progressive decrease in the sealing of the closure of the passage, the elastomeric seal becoming increasingly permeable, particularly at high temperatures, for example up to 180 degrees Celsius (° C.).